Conditional expression of a humanized NPM1c knock-in allele in the hematopoietic system (mediated by Mx1-iCre) resulted in the development of late onset AML in about 30% of the mice, however this percentage increased to 80% following the activation of cooperating proto-oncogenes through the use of the Sleeping Beauty insertional mutagenesis system [46]. Here, MX1 is linked to acute myeloid leukemia.